Method of preparing calcium soap-calcium salt greases



United States Patent Int. Cl. C10m /16 US. Cl. 252-36 16 Claims ABSTRACT OF THE DISCLOSURE A calcium soap-calcium salt grease composition is prepared by the following sequence of steps:

(1) Form a first lime-oil slurry of calcium oxide and/ or calcium hydroxide and a major amount of the mineral lubricating oil used in preparing the grease.

(2) Add acetic acid to the first lime-oil slurry without the application of external heat.

(3) Add a high molecular weight carboxylic acid, e.g., 'stearic acid, to the first lime-oil slurry without the application of external heat.

(4) Add a medium molecular weight carboxylic acid, e.g.,.caprylic acid, to the first lime-oil slurry without the application of external heat.

(5) Form a second lime-oil slurry of calcium oxide and the remainder of the mineral lubricating oil used in preparing the grease.

(6) Add the second lime-oil slurry to the first lime-oil slurry.

(7) Heat the slurry mixture to 300 to 325 F.

(8) Add a metal acetate, e.g., lead acetate, to the heated slurry mixture.

(9) Heat the slurry mixture to 450 to 460 F. to effect dehydration of the grease.

(10) Cool the grease composition to below 200 F.

(11) Mill the cooled grease composition to obtain a smooth-textured grease product.

Thli invention relates to a lubricating grease composition which contains the calcium salt of acetic acid, the calcium salt of a medium molecular weight carboxylic acid and the calcium soap of a high molecular weight carboxylic acid, and more particularly to an improved method for preparing such a grease composition.

Increased production rates have placed increased loads on existing machinery and particularly on the bearings of such machinery/With increased loads on machinery, bearings are subjected to greater frictional forces with the evolution of large amounts of heat, causing the bearings to operate at temperatures above those which would normally be encountered. While heat caused from frictional forces is a problem in lubricating all bearings, the problem is even greater when the bearings are also subjected to heat from external sources. Thus, the lubrication of bearings in equipment handling hot materials such as in steel rolling mills, paper mills and the like requires a lubricating grease capable of withstanding very high temperatures.

One of the problems encountered in lubricating bearings operating at very high temperatures is .the provision of a grease composition which will remain semi-solid when subjected to these high temperatures. A semi-solid structure is desirable to prevent the loss of grease by leakage from the bearing, thereby causing the scoring of bearings due to inadequate lubrication. Inasmuch as many bearings operate at temperatures in the order of 400 to 500 F. and higher, a grease for lubricating such bearings should have a low penetration and a high dropping point, i.e., a dropping point of at least about 500 F. Such a grease should also be one that can be produced economically.

It is known in the art that high temperature greases are obtainable by thickening lubricating oils to the consistency of a grease with various combinations of soaps and salts. According to the disclosure in United States Patent No. 2,197,263 which issued on Apr. 16, 1940 to E. S. Carmichael, a lime base grease of improved thermal stability is obtained by employing calcium acetate in combination with the calcium soap of a higher fatty acid. More recently, improved high temperature, water resistant greases have been obtained by utilizing soap-salt complexes comprising the calcium salt of acetic acid, the calcium salt of a medium molecular weight carboxylic acid and the calcium soap of a high molecular weight carboxylic acid. While high temperature greases thickened with such soapsalt complexes are obtainable, difficulty has been encountered in manufacturing these greases using conventional grease-making procedures because of excessive foaming which has been encountered and also because of widely varied physical properties which have occurred from batch to batch. Also, the application of heat from external sources has been required in order that the temperature in the grease-making vessel will be above the melting point of the reactants. Since many of the higher fatty acids used in making greases melt at temperatures above F., the application of heat has been required to assure a temperature at least this high, i.e., a temperature above the melting point of the acid during the saponification of the acid. Since acetic acid boils at a relatively low temperature and tends to steam distill at temperatures below its boiling point, a portion of the acetic acid is frequently lost by evaporation in open kettle manufacturing processes if the temperature at the time of adding acetic acid is high enough to maintain the high molecular weight acids in a liquid state. Evaportion of the acetic acid is undesirable not only from the standpoint of economics but also from the problem of foaming which is caused at least in part by the escape of the acid from the reaction mass. Naturally, if uncontrolled evaporation of the acetic acid occurs, the properties of the grease will vary from batch to batch because of the varied content of the salt of the acetic acid in the finished grease composition.

In accordance with the present invention an improved process is provided for economically producing a soap-salt grease composition having physical properties within desired limits from batch to batch, said process utilizing a temperature above the melting point of the high molecular weight carboxylic acid without the application of heat from an external source during the initial phase of the process, with little or no evaporation of the acedic acid and with little or no foaming during the preparation of the grease. In the process of the invention two lime-oil slurries are employed. The lime in the first lime-oil slurry can be calcium hydrate, calcium oxide or mixtures thereof. The lime in the second lime-oil slurry must be calcium oxide if maximum hardness is desired for a given amount of oil thickener.

I have found that if substantially all of the mineral oil which is ultimately required in the grease composition is utilized in forming a first lime-oil slurry with calcium hydrate or calcium oxide or mixtures thereof and if all of the actic acid is added to the first lime-oil slurry prior to adding the high molecular weight carboxylic acid and the medium molecular weight carboxylic acid and if the remainder of the mineral oil ultimately required in the grease composition is used in making a second lime-oil slurry with calcium oxide, a high temperature grease can be obtained having physical properties within desired limits from batch to batch without excessive foaming during the manufacture. of the grease.

The process of the invention is economically attractive in that the heat developed during the addition of the acetic acid to the first lime-oil slurry raise the temperature of the first lime-oil slurry to such an extent that no heat is required from an outside source to raise the temperature of the first lime-oil slurry above the melting point ofthe high molecular weight carboxylic acid. Thus, in accordance with the present invention a smooth-textured high temperature calcium soap-calcium salt grease composition can be obtained without excessive foaming during its preparation by a process which comprises forming a homogeneous first lime-oil slurry of a calcium compound selected from the group consisting of calcium oxide and calcium hydroxide and a major amount of the mineral lubricating oil used in preparing the finished grease composition, the amount of the calcium compound in the first lime-oil slurry being stoichiometrically sufficient to completely neutralize all of the acids to be added in subsequent steps of the process; gradually adding acetic acid with agitation without the application of external heat to the homogeneous first lime-oil slurry until all of the acetic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the acetic acid has reacted with the first lime-oil slurry, the heat evolved in the reaction of the acetic acid with the first lime-oil slurry 'being sufiicient to raise the temperature of the reaction mass above the melting point of the high molecular weight carboxylic acid to be added in the next step of the process; gradually adding the high molecular weight carboxylic acid with agitation without the application of external heat to the first lime-oil slurry which has reacted with aceticacid until all of the high molecular weight carboxylic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the high molecular weight carboxylic acid has reacted with the first lime-oil slurry containing reacted acetic acid; gradually adding a medium molecular weight carboxylic acid with agitation without the application of external heat to the first lime-oil slurry which has reacted with acetic acid and with the high molecular weight carboxylic acid until all of the medium molecular carboxylic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the medium molecular weight carboxylic acid has reacted with the first lime-oil slurry containing reacted acetic acid and reacted high molecular weight carboxylic acid; forming a homogeneous second lime-oil slurry of calcium oxide and the remainder of the mineral lubricating oil used in preparing the finished grease composition, the amount of the calcium oxide being sufficient to react with any unreacted acid and to result in a stoichiometric excess alkalinity of about 0.5 to about 1 percent as calcium oxide (about 0.7 to about 1.3 percent as calcium hydroxide); adding the second lime-oil slurry of calcium oxide and mineral lubricating oil to the first lime-oil slurry which has reacted with acetic acid, the high molecular weight carboxylic acid and the medium molecular weight carboxylic acid; heating the slurry mixture thus formed to a temperature of about 300 to about 325 F. to effect substantially complete saponification of the acids; adding a metal acetate selected from the group consisting of lead acetate and zinc acetate to the heated slurry mixture in an amount sufiicient to give a grainy mixture; heating the mixture to a temperature of about 450 to about 460 F. with agitation until a homogeneous grainy, dehydrated grease product is obtained; cooling the grainy, dehydrated grease product to a temperature below about 200 F.; and milling the cooled grease product to obtain a smooth-textured calcium soap-calcium salt grease composition.

The mineral lubricating oil employed in the present process can be any of the hydrocarbon oils of lubricating grade customarily used in compounding greases. The oil may be refined or semi-refined, paraflinic-naphthenic-, or asphaltic-base oil having a viscosity of about 50 to about 4000 SUS at 100 F. If desired, a blend of oils of suitable viscosity may be employed instead of a single oil by means of which any desired viscosity within the range of about 50 to about 4000 SUS at 100 F. may be secured. In producing a multipurpose lubricant, it is generally preferred to employ an oil having a viscosity within the range of about 300 to about 1000 SUS at 100 F.

The mineral lubricating oil content of grease compositions prepared according to this invention comprises about 60 to about percent by weight of the finished grease composition. About to about 99 percent by weight of the mineral lubricating oil used in preparing the finished grease is utilized in preparing the first limeoil slurry. The remainder of the mineral lubricating oil, i.e., about 1 to about 10 percent by weight of the total amount of mineral lubricating oil is utilized in preparing the second lime-oil slurry. The particular oil or oil blend, as well as the exact amount of oil employed, depends, of course, upon the characteristics desired in the finished grease. The soap-salt content of grease compositions prepared by the invention comprises about 15 to about 40 percent by weight of the finished grease composition. the process of the present invention are those having about ylic acids of high, medium and low molecular weights. The acids are those normally used in preparing greases by thickening lubricating oils with soap-salt complexes. The low molecular weight carboxylic acid is acetic acid. The acid can be any grade of commercially available acid. Glacial acetic acid is used in a preferred embodiment. The amount of the acetic acid which is employed is an amount such that the calcium salt thereof will comprise about 10 to about 25 percent by weight of the finished grease.

The high molecular weight carboxylic acids useful in the process of the present invention are those having about 13 to about 32 carbon atoms per molecule and preferably those having 18 to 22 carbon atoms per molecule or a mixture containing two or more such acids or their glycerides such as those obtained from various fatty oils such as cottonseed oil, rapeseed oil, castor oil, animal oils, fish oils and the like. The carboxylic acids can be either saturated or unsaturated or mixtures thereof. The fatty acids normally used in the manufacture of conventional greases, particularly the saturated fatty acids, are preferred. Exemplary of the fatty acids which can be used in the process of the invention are tridecanoic, myristic, palmitic, stearic, 12-hydroxy stearic, oleic, linoleic, linolenic, arachidic, arachidonic, behenic, lignoceric, cerotic and the like. In some instances it is desirable to hydrogenate a fatty acid mixture in order to increase the saturation of the acids in the mixture. Thus, the fatty acids may be those derived from hydrogenated oils of vegetable, animal and marine extraction. Hydrogenated fish oil fatty acids, hydrogenated tallow fatty acids and hydrogenated castor oil fatty acids and, in general, any hydrogenated animal or vegtable oil which contains a fatty acid having more than 12 carbon atoms can be used. I prefer to employ mixtures of acids such as those ob tained from beef tallow or hydrogenated castor oil or a mixture of these glycerides. Hydrogenation of the fatty acids and/or fatty oils is not a part of this invention but can be carried out by various known processes such as for example, the process described on pages 372 to 430 of Hydrogenation of Organic Substances 3rd edition, by Carleton Ellis, D. Van Nostrand Co, Inc., New York (1930).

The amount of the high molecular weight carboxylic acid used in the process of the invention depends upon the amount of the corresponding calcium soap which is desired in the finished grease. And, the amount of the calcium soap in the finished grease depends upon the properties desired in the finished grease. In general, the high molecular weight carboxylic acid is employed in an amount such that the calcium soap thereof comprises about 2 to about percent by weight of the finished grease.

The medium molecular weight carboxylic acid which is employed in the present invention can be either a sub stantially pure fatty acid having about 7 to about 12 carbon atoms preferably 8 to 10 carbon atoms per molecule or a mixture containing two or more of such acids. Exemplary of the medium molecular weight carboxylic acids which can be used in the process of the invention are heptanoic, caprylic, pelargonic, capric and lauric. Of these acids caprylic acid is preferred particularly when the high molecular weight carboxylic acid is stearic acid.

The amount of the medium molecular weight carboxylic acid used in the process of the invention depends somewhat on the properties desired in the finished grease. In general, the medium molecular weight carboxylic acid is employed in an amount such that the calcium salt thereof comprises about 2 to about 10 percent by weight of the finished grease.

The grease composition prepared in accordance with the process of the present invention is one in which the acetic acid is employed in an amount considerably above the amounts of the medium and high molecular weight carboxylic acids. Thus, in a preferred embodiment, 7 to 8 parts by weight of glacial acetic acid are used for each part by weight of stearic acid and caprylic acid. Exemplary of the molar ratios of the acids used in the process of the present invention are as follows:

Acids: Molar ratio Acetic: High molecular weight :1-30:l Acetic: Medium molecular weight 10:1-20z1 Acetic: High molecular weight plus medium molecular weight 10:1-25 :1

While grease compositions prepared in the process of the present invention have molar amounts of acetic acid from 10 to 30 times the amount of each of the other acids, the other acids can be used in various proportions with respect to each other. Thus, the molar ratio of medium molecular weight to high molecular weight carboxylic acid can be between about 10:1 and 1: 10. In one embodiment of the invention using acetic, stearic and caprylic acids, the following molar ratios have given an excellent high temperature grease:

Acids: Molar ratio Acetic acidzStearic acid 29:1 Acetic acidzCaprylic acid 15.7:1 Acetic acidzStearic acid plus caprylic acid 11.4:1 Caprylic acidzStearic acid 19:1

The lime employed in preparing the lime-oil slurries for use in the process of the invention can be commercial grease-making grades of calcium hydroxide or calcium oxide. In preparing the first lime-oil slurry, the lime can be calcium hydroxide, calcium oxide or a mixture of calcium hydroxide and calcium oxide. When a mixture of calcium hydroxide and calcium oxide is used the weight ratio of the two calcium compounds with respect to each other can vary Widely. Thus, ratios of these compounds can vary from 1:20 to 20:1, more or less, and give satisfactory results. A grease of maximum hardness has been obtained with equal weights of calcium hydroxide and calcium oxide in the first lime-oil slurry. The amount of the calcium compound employed in the first lime-oil slurry is stoichiometrically sufficient to react with all of the acids used in preparing the grease composition. The lime used in preparing the second lime-oil slurry must be calcium oxide if a grease of maximum hardness is to be obtained from a given amount of calcium compound. The amount of the calcium oxide employed in the second lime-oil slurry is sufiicient to react with any unreacted acid and also is sufficient to result in a grease composition having an excess alkalinity of about 0.5 to about 1 percent as calcium oxide. This alkalinity corresp'onds to about 0.7 to about 1.3 percent calculated as calcium hydroxide.

The metal acetate which is employed in accordance with the process of the invention is selected from the group consisting of lead and zinc acetates. These acetates promote maximum crystalline formation of the complex thickener. Although other metallic acetates could be substituted for the acetates of lead and zinc, these acetates and particularly lead acetate is preferred for an observed thin fihn property and distinct color tone imparted to the finished grease. The amount of the lead or zinc acetate employed is a small amount sufiicient to impart a grainy structure to the grease prior to being milled. The grainy structure disappears upon subsequent milling of the grease. The amount of metal acetate is normally about 0.05 to 3 percent by Weight of the finished grease. Good results have been obtained with 0.1 percent by weight of lead acetate.

The lubricating grease compositions produced according to the invention can contain minor amounts of other agents normally added to grease compositions to improve one or more specific properties thereof. Thus, the grease compositions can contain an antioxidant, a dispersant, an emulsifier, a corrosion and rust inhibitor, an extreme pressure agent, a metal deactivator, a tackiness agent, a dye and the like. Whether or not such additives are employed and the amounts thereof depend. to a large extent upon the severity of the conditions to which the composition is subjected. When such conventional additives are used they are generally added in amounts between about 0.01 and about 5 percent by weight based on the weight of the total composition. They may be added prior, during or after the heating steps depending upon the thermal stability of the particular additive employed as will be apparent to those skilled in the art.

The process of the invention is illustrated by the following specific example wherein all of the parts are parts by weight.

A lime-oil slurry is prepared by charging 15 parts of a mineral lubricating oil having a viscosity of about 600 SUS at F. and 9.777 parts of hydrated lime [Ca(OH) into an open saponification kettle at about 70-80 F. The oil and lime mixture is stirred without the application of heat until a smooth mixture is obtained. An additional 55 parts of the mineral lubricating oil (600 SUS at 100 F.) are then added to the kettle, the contents of which are stirred without heating to obtain a homogeneous first lime-oil slurry. Glacial acetic acid (14.43 parts) is added in four about equal increments to the first lime-oil slurry with stirring and without the application of heat. Stirring is continued until a maximum temperature rise is noted. The heat of reaction causes the temperature of the contents in the vessel to rise to about 170-l80 F. This temperature is below the boiling point of acetic acid and above the melting point of stearic acid which is added in. the next step of the process. Stearic acid (2.35 parts) is gradually added to the saponification kettle with stirring and without the application of external heat. When the stirred mixture appears to be homogeneous, 2.21 parts of caprylic acid is gradually added to the reaction vessel with stirring and Without the application of heat. A second lime-oil slurry consisting of 0.833 part of calcium oxide in 2.5 parts of mineral oil (600 SUS at 100 F.) is then prepared and thoroughly mixed with the contents of the vessel. The maximum temperature reached at any time during the preceding charging operation is below 200 F. The excess lime at this point is 1.1 percent as calcium hydroxide or 0.833 percent as calcium oxide. With continuous stirring, heat is applied to the kettle to raise the temperature of the contents to about 300 to about 325 F. When this temperature is reached, 0.1 part of lead acetate is added. The contents of the kettle are then further heated with stirring until a temperature of about 450460 F. is reached. The temperature is held at this maximum for about 1 hour or until dehydration is substantially complete. Little or no foaming is evidenced during dehydration. The contents of the kettle are then cooled. Twitchell 8266 Base (1.5 parts) is added as an emulsifying and anti-corrosion agent when the temperature drops to about 325 335 F. Twitchell 8266 Base is a concentrate of sodium sulfo-carboxylate (6 parts) and sodium petroleum sulfonate (52 parts) in mineral oil (42 parts). Upon further cooling to about 215225 F., the condensation product of formaldehyde and N,N-dimethylaniline (0.8 part) is added as an antioxidant. Upon cooling still further to a temperature of about 180 F., a grease product is obtained. At this point, the product has a grainy texture. Upon subsequent milling in a conventional grease mill, a smooth-textured high temperature calcium soapcalcium salt grease is obtained.

The approximate make-up and properties of a grease composition prepared in accordance with the process of the invention as described above are as follows:

Grease composition: Percent by weight Mineral lubricating oil (600 SUS at 100 F.) 72.5 Calcium acetate 19.0 Calcium soap of stearic acid 2.5 Calcium salt of caprylic acid 2.5 Excess alkali as Ca(OH) 1.1 Lead acetate 0.1 Condensation product of formaldehyde and N,N-dimethylaniline a 0.8 Twitchell 8266 Base 1.5 Inspection:

Dropping point, ASTM D566: F 500+ Penetration, ASTM D217 Unworked 284 Worked 60 strokes 322 Worked 100,000 strokes 323 Corrosion test, ASTM D1743 Rating 1 Oxidation stability, ASTM D942- 100 hours 1 500 hours 4 Antioxidant. Emulsifying and anti-corrosion agent.

In accordance with the process of the invention a grease composition is prepared using two lime-oil slurries. In the first lime-oil slurry, the amount of lime employed is stoichiometrically sufiicient to completely neutralize the acetic acid and the medium and high molecular weight carboxylic acids which are added in subsequent steps of the process. The lime in the first lime-oil slurry can be either calcium hydroxide or calcium oxide. In the second lime-oil slurry, the amount of lime is sufficient to react with any unreacted acid and to result in a stoichiometric excess alkalinity. The lime in the second lime-oil slurry is calcium oxide.

In order to illustrate the importance of using a twoslurry process to obtain a grease composition having a low penetration from a given amount of oil and oil thickener, compositions were prepared from identical amounts of oil, acetic acid, stearic acid, caprylic acid and lime, the only difference being that the total amount of lime required for neutralization and excess alkalinity (calcium hydrate for neutralization and calcium oxide for excess alkalinity) was added at one time in the oneslurry process. In the two-slurry process, the stoichiometric amount of calcium hydrate required to neutralize the acids was added in the first lime-oil slurry. In the second lime-oil slurry the amount of calcium oxide employed was only that amount required to give excess alkalinity. The following is a tabulation of the worked penetration (60 strokes) obtained in the grease compositions prepared by the two methods.

8 Method: Worked penetration One-slurry procedure 397 Two-slurry procedure 332 It will be noted that the two-slurry procedure gives a grease composition having 65 penetration units lower than the grease composition prepared by the one-slurry procedure.

In order to illustrate the importance of using calcium oxide in the second lime-oil slurry of the two-slurry process to obtain a grease composition having a low penetration from a given amount of oil and oil thickener, compositions were prepared from identical amounts of oil, acetic acid, stearic acid, caprylic acid and lime, the only difference being that the lime in the first lime-oil slurry was calcium hydroxide, calcium oxide or mixtures thereof and the lime in the second lime-oil slurry was either calcium hydroxide or calcium oxide. In each case the lime added in the first lime-oil slurry was stoichiometrically sufficient to neutralize all of the acids. The lime added in the second lime-oil slurry was sufi icient to give an excess alkalinity of 1.1 as Ca(OH) The following is a tabulation of the worked penetration (60 strokes) obtained in the grease compositions prepared under comparative conditions.

TWO-SLURRY METHOD and calcium oxide (2:1 weight ratio).

It will be noted that in the two-slurry method, harder grease compositions are obtained when the lime component of the second lime-oil slurry is calcium oxide regardless of whether the lime in the first lime-oil slurry is calcium hydroxide, calcium oxide or a mixture of calcium hydroxide and calcium oxide. It will be noted that the hardest grease is obtained when the lime in the first lime-oil slurry is a mixture of calcium hydroxide and calcium oxide (1:1 weight ratio) and the lime in the second lime-oil slurry is calcium oxide.

While my invention has been described with reference to various specific examples and embodiments, it will be understood that the invention is not limited to such examples and embodiments and may be variously practiced within the scope of the claims hereinafter made.

I claim:

1. A method of preparing a smooth-textured high temperature calcium soap-calcium salt grease composition which comprises forming a homogeneous first lime-oil slurry of a calcium compound selected from the group consisting of calcium oxide and calcium hydroxide and a major amount of the mineral lubricating oil used in preparing the finished grease composition, the amount of the calcium compound in the first lime-oil slurry being stoichiometrically sufficient to completely neutralize all of the acids to be added in subsequent steps of the process; gradually adding acetic acid with agitation without the application of external heat to the homogeneous first lime-oil slurry until all of the acetic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the acetic acid has reacted with the first lime-oil slurry, the heat evolved in the reaction of the acetic acid with the first lime-oil slurry being sufficient to raise the temperature of the reaction mass above the melting point of the high molecular weight carboxylic acid to be added in the next step of the process; gradually adding the high molecular weight carboxylic acid with agitation without the application of external heat to the first lime-oil slurry which has reacted with acetic acid until all of the high molecular weight carboxylic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the high molecular weight carboxylic acid has reacted with the first lime-oil slurry containing reacted acetic acid; gradually adding a medium molecular weight carboxylic acid with agitation without the application of external heat to the first lime-oil slurry which has reacted with acetic acid and with the high molecular weight carboxylic acid until all of the medium molecular weight carboxylic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the medium molecular weight carboxylic acid has reacted with the first lime-oil slurry containing reacted acetic acid and reacted high molecular weight carboxylic acid; forming a homogeneous second lime-oil slurry of calcium oxide and the remainder of the mineral lubricating oil used in preparing the finished grease composition, the amount of calcium oxide being sufiicient to react with any unreacted acid and to result in a stoichiometric excess alkalinity of about 0.5 to about 1 percent as calcium oxide; adding the second lime-oil slurry of calcium oxide and mineral lubricating oil to the first lime-oil slurry which has reacted with acetic acid, the high molecular weight carboxylic acid and the medium molecular weight carboxylic acid; heating the slurry mixture thus formed to a temperature of about 300 to about 325 F. to effect substantially complete saponification of the acids; adding a metal acetate selected from the group consisting of lead acetate and zinc acetate to the heated slurry mixture in an amount sufficient to give a grainy mixture; heating the mixture to a temperature of about 450 to about 460 F. with agitation until a homogeneous grainy, dehydrated grease product is obtained; cooling the grainy, dehydrated grease product to a temperature below about 200 F.; and milling the cooled grease product to obtain a smooth-textured calcium soap-calcium salt grease composition.

2. The method of claim 1 wherein the high molecular weight carboxylic acid contains 13 to 32 carbon atoms and the medium molecular weight carboxylic acid contains 7 to 12 carbon atoms.

3. The method of claim 1 wherein the high molecular Weight carboxylic acid is stearic acid and the medium molecular weight carboxylic acid is caprylic acid.

4. The method of claim 1 wherein the molar ratio of the acids are within the following limits:

Acids: Molar ratio Acetic: High molecular weight 15 :1-30zl Acetic: Medium molecular weight :120:1 Acetic: High molecular weight plus medium molecular weight 10:1-25 :1

5. The method of claim 1 wherein the calcium compound in the first lime-oil slurry is a mixture of calcium hydroxide and calcium oxide. I

6. The method of claim 5 wherein the weight ratio of calcium hydroxide to calcium oxide is about 1:20 to 20:1.

7. The method of claim 5 wherein the weight ratio of calcium hydroxide to calcium oxide is about 1:1.

8. The method of claim 1 wherein the calcium compound in the first lime-oil slurry is calcium hydroxide.

9. The method of claim 1 wherein the calcium compound in the first lime-oil slurry is calcium oxide.

10. A method of preparing a smooth-textured high temperature calcium soap-calcium salt grease composition which comprises forming a homogeneous first limeoil slurry of calcium hydroxide and a major amount of the mineral lubricating oil used in preparing the finished grease composition, the amount of the calcium hydroxide being stoichiometrically sufficient to completely neutralize all of the acids to be added in subsequent steps of the process; gradually adding acetic acid with agitation Without the application of external heat to the homogeneous first lime-oil slurry until all of the acetic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the acetic acid has reacted with the first lime-oil slurry, the heat evolved in the reaction being sufficient to raise the temperature of the reaction mass to about 170 to about 180 F.; gradually adding stearic acid with agitation without the application of external heat to the first lime-oil slurry which has reacted with acetic acid until all of the stearic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the stearic acid has reacted with the first lime-oil slurry containing reacted acetic acid; gradually adding caprylic acid with agitation without the application of external heat: to the first limeoil slurry which has reacted with acetic acid and with stearic acid until all of the caprylic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the caprylic acid has reacted with the first lime-oil slurry containing reacted acetic acid and reacted stearic acid; forming a homogeneous second lime-oil slurry of calcium oxide and the remainder of the mineral lubricating oil used in preparing the finished grease composition, the amount of calcium oxide being sufficient to react with any unreacted acid and to result in a stoichiometric excess of alkalinity of about 0.5 to about 1 percent as calcium oxide; adding the second lime-oil slurry of calcium oxide and mineral lubricating oil to the first lime-oil slurry which has reacted with acetic acid, stearic acid and caprylic acid; heating the slurry mixture thus formed to a temperature of about 300 to about 325 F. to efiect substantially complete saponification of the acids; adding about 0.05 to about 3 percent by weight of lead acetate to the heated slurry mixture; heating the mixture to a temperature of about 450 to about 460 F. with agitation until a homogeneous grainy, dehydrated grease product is obtained; cooling the grainy, dehydrated grease product to a temperature below about 200 F.; and milling the cooled grease product to obtain a smoothtextured calcium soap-calcium salt grease composition.

11. The method of claim 10 wherein the mineral oil content of the grease composition comprises about 60 to about percent by weight to the finished composition and the soap-salt content of the grease composition comprises about 15 to about 40 percent by weight of the finished grease composition.

12. The method of claim 10 wherein the mineral oil content of the grease composition comprises about 60 to about 85 percent by weight of the finished grease composition, the calcium salt of acetic acid comprises about 10 to about 25 percent by weight of the finished grease composition, the calcium soap of stearic acid comprises about 2 to about 10 percent by weight of the finished grease composition and the calcium salt of caprylic acid comprises about 2 to about 10 percent by weight of the finished grease composition.

13. A method of preparing a smooth-textured high temperature calcium soap-calcium salt grease composition which comprises forming a homogeneous first limeoil slurry of calcium hydroxide and a major amount of the mineral lubricating oil used in preparing the finished grease composition, the amount of the calcium hydroxide being stiochiometrically suificient to completely neutralize all of the acids to be added in subsequent steps of the process; gradually adding acetic acid with agitation with out the application of external heat to the homogeneous first lime-oil slurry until all of the acetic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the acetic acid has reacted with the first lime-oil slurry, the heat evolved in the reaction being sutficient to raise the temperature of the reaction mass to about to about 180 F.; gradually adding stearic acid with agitation without the application of external heat to the first limeoil slurry which has reacted with acetic acid until all of the stearic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the stearic acid has reacted with the first lime-oil slurry containing reacted acetic acid; gradually adding caprylic acid with agitation without the application of external heat to the first lime-oil slurry which has reacted with acetic acid and with stearic acid until all of the caprylic acid employed in preparing the grease composition has been added, the agitation being continued until a substantial portion of the caprylic acid has reacted with the first lime-oil slurry containing reacted acetic acid and reacted stearic acid; forming a homogeneous second lime-oil slurry of calcium oxide and the remainder of the mineral lubricating oil used in preparing the finished grease composition, the amount of calcium oxide being sufficient to react with any unreacted acid and to result in a stoichiometric excess alkalinity of about 0.5 to about 1 percent as calcium oxide; adding the second lime-oil slurry of calcium oxide and mineral lubricating oil to the first lime-oil slurry which has reacted with acetic acid, stearic acid and caprylic acid; heating the slurry mixture thus formed to a temperature of about 300 to about 325 F, to effect substantially complete saponification of the acids; adding about 0.05 to about 3 percent by weight of lead acetate to the heated slurry mixture; heating the mixture to a temperature of about 450 to about 460 F. with agitation until a homogeneous grainy, dehydrated grease product is obtained; cooling the grainy, dehydrated grease product to about 325 F. and adding an emulsifying and anti-corrosion agent; further cooling the grease product to about 215 to about 225 F. and adding an oxidation inhibitor; further cooling the grease product to a temperature below about 200 F.; and milling the cooled grease product to obtain a smoothtextured calcium soap-calcium salt grease composition.

14. The method of claim 13 wherein the mineral oil content of the grease composition comprises about 60 to about 85 percent by weight of the finished grease composition, the calcium salt of acetic acid comprises about 10 to about 25 percent by weight of the finished grease composition, the calcium soap of stearic acid comprises about 2 to about 10 percent by weight of the finished grease composition, the calcium salt of caprylic acid comprises about 2 to about 10 percent by weight of the finished grease composition and the emulsifying and anti-corrosion agent and the oxidation inhibitor comprise about 0.01 to about 5 percent by weight of the finished grease composition.

15. The method of claim 13 wherein the mineral oil content of the grease composition comprises about 72.5 parts by weight of the finished grease composition, the calcium salt of acetic acid comprises about 19 parts by weight of the finished grease composition, the calcium soap of stearic acid comprises about 2.5 parts by weight of the finished grease composition, the calcium salt of caprylic acid comprises about 2.5 parts by weight of the finished grease composition, the emulsifying and anticorrosion agent comprises about 1.5 parts by weight of the finished grease composition, the oxidation inhibitor comprises about 0.8 part by weight of the finished grease composition and the excess of alkalinity is 1.1 percent as calcium hydroxide.

16. The method of claim 15 wherein parts of the 72.5 parts of mineral oil are added in the first lime-oil slurry and 2.5 parts of the 72.5 parts of mineral oil are added in the second lime-oil slurry.

References Cited UNITED STATES PATENTS 2,850,458 9/1958 Beerbower et a1. 25239 2,976,242 3/1961 Morway 25239 3,170,879 2/1965 Butcosk 252-39 DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner U.S. Cl. X.R. 252-39 73,133 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 245 Dated September 9, 1969 Inventor-( arl M. Peck It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 52, 'acedic" should read acetic line 64, "actic" should read acetic Column 4, lines 25 and 26, the sentence "the process of the present invention are those having about ylic acids of high, medium and low molecular weights should start a new paragraph and should read The process of the present invention utilizes carboxylic acids of high, medium and low molecular weights SI'GNED AND SEALED MAY 5 9 (S a m A mm In W El my JR. Anestinfi Gemin or Patmts 

